The instant invention relates to printing apparatus and more particularly to an apparatus for applying images to opposite sides of a continuous strip at spaced printing stations and to a print head mounting assembly for the apparatus.
A number of different types of printing apparatus have been heretofore available for applying images to the opposite sides of continuous strips. In this regard, heretofore printing apparatus of this general type have been widely available and have been used for a variety of applications, including printing continuous strips of labels, tags, and the like for retail sales applications. However, it has been found that it can be extremely difficult to coordinate the printing operations which take place at the different printing stations of apparatus of this type to assure that the longitudinal positions of the images which are applied to the opposite sides of continuous strips are properly oriented with respect to each other. It has also been found that errors in the longitudinal positions of the images which are applied to the opposite sides of continuous strips often tend to be cumulative so that the effects of minute errors are greatly magnified during prolonged printing processes.
The instant invention provides an effective printing apparatus which overcomes the above described difficulties of the heretofore available printing apparatus for applying images to the opposite sides of continuous strips. Specifically, the instant invention provides an apparatus for applying images to the opposite sides of a continuous strip so that the longitudinal positions of the images are precisely coordinated along substantially the entire extent of the strip. More specifically, the apparatus of the instant invention comprises first printing means actuatable for applying a first image to a first side of a continuous strip at a first printing station, second printing means actuatable for applying a second image to the opposite or second side of the continuous strip at a second printing station which is a predetermined distance from the first printing station, and drive means including a rotatable drive roller for longitudinally advancing the continuous strip so that it passes in a substantially taut disposition from the first printing station to the second printing station upon rotation of the drive roller. The apparatus further comprises stepping motor means rotatable at a predetermined rate of stepped rotational increments per revolution for rotating the drive roller to advance the strip and control means operative for actuating the first and second printing means to apply images to the opposite sides of the strip, the control means being responsive to a predetermined number of stepped rotational increments of the stepping motor means which corresponds to the distance between the first and second printing stations for coordinating the longitudinal positions of the images which are applied to the strip at the first and second printing stations. The apparatus of the instant invention is preferably embodied as a thermal printing apparatus, and the first printing means preferably comprises a first thermal print head at the first printing station and means for advancing a first thermal printing film to the first printing station so that the first printing film is interposed in engagement between the first thermal print head and the first side of the strip at the first printing station. The second printing means preferably comprises a second thermal print head at the second printing station and means for advancing a second thermal printing film to the second printing station so that the second thermal printing film is interposed in engagement between the second thermal print head and the second side of the strip at the second printing station. The first and second printing means preferably comprises first and second platens at the first and second printing stations, respectively, and means biasing the first and second print heads toward the first and second platens, respectively. Further, the strip and the first thermal printing film pass between the first print head and the first platen at the first printing station, and the strip and the second printing film pass between the second print head and the second platen at the second printing station.
The preferred form of the apparatus of the instant invention which is embodied as a thermal printing apparatus further comprises first and second print head mounting assemblies for mounting the first and second thermal print heads, respectively, so that they are biased toward the first and second platens, respectively, at the first and second printing stations, respectively. The mounting assemblies preferably each comprise toggle means including at least two pivotably connected toggle elements which are alternatively positionable in actuated positions wherein they are releasably secured in substantially aligned relation and unactuated positions wherein they are in nonaligned relation and freely pivotable with respect to each other. Each of the mounting assemblies preferably further comprises biasing means communicating with the print head thereof through the toggle elements thereof when the toggle elements are in the actuated positions thereof for biasing the print head thereof toward its respective platen. Each of the mounting assemblies preferably further comprises a mounting frame which is pivotably mounted in the printing apparatus, and the print head of each of the mounting assemblies is mounted on the mounting frame thereof so that it is pivotable therewith away from its respective platen when the toggle elements thereof are in the unactuated positions thereof. Still further, the preferred form of the apparatus preferably comprises means responsive to movement of the toggle elements thereof from the actuated positions to the unactuated positions for advancing the respective thermal printing film thereof a predetermined amount so that the film is maintained in a substantially taut disposition when the toggle elements are moved to the unactuated positions thereof.
It has been found that the printing apparatus of the instant invention has specific advantages over the heretofore available printing apparatus. Specifically, the printing apparatus of the instant invention is operative for applying images to opposite sides of a continuous strip so that the longitudinal positions of the images are precisely coordinated along substantially the entire longitudinal extent of the strip. In this regard, the apparatus of the instant invention is operative with stepping motor means which is rotatable at a predetermined rate of stepped rotational increments per revolution for rotating the drive roller to advance the strip through the apparatus. The stepping motor means is inherently self-correcting on each revolution so that each revolution of the stepping motor includes exactly the same number of stepped rotational increments. Further, the means responsive to the stepping motor means for actuating the first and second printing means is responsive to a predetermined number of stepped rotational increments which corresponds to the distance between the first and second printing stations. Accordingly, the apparatus is operative for precisely coordinating the positions of the images which are applied to the opposite sides of a strip; and since the means for actuating the printing means is responsive to a predetermined number of stepped rotational increments rather than a predetermined passage of time, the apparatus is operative without cumulative errors in the longitudinal positions of the images.
The mounting assembly of the instant invention also has significant advantages over the heretofore available mounting assemblies for thermal printing apparatus. Specifically, the mounting assembly of the instant invention is operative with a toggle action between an actuated position wherein the print head thereof is biased toward the adjacent platen and an unactuated position wherein the print head thereof is moved away from the platen and the biasing means is released so that the print head is freely movable. Further, the apparatus includes means for advancing a thermal printing film a predetermined amount when the respective toggle members thereof are moved to the unactuated positions. Accordingly, when the toggle members are moved to the unactuated positions thereof, the thermal printing film is maintained in a taut disposition to provide clear access to the respective printing station.
Accordingly, it is a primary object of the instant invention to provide a printing apparatus for applying images to the opposite sides of a continuous strip wherein the longitudinal positions of the images on the opposite sides of the strip are precisely coordinated.
Another object of the instant invention is to provide a printing apparatus for applying images to the opposite sides of a continuous strip wherein the strip is advanced between first and second printing stations utilizing a stepping motor driven advancement system.
A still further object of the instant invention is to provide an improved print head mounting assembly for a thermal printing apparatus.
An even further object of the instant invention is to provide an effective thermal print head mounting assembly which is movable to an unactuated position for moving a print head away from its respective platen.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.